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Astronomy 251
Life on Other Worlds
Mondays 4-6, MP102
Prof. Ray Jayawardhana
MP 1408 416 946 7291 [email protected]
Office hours: Tuesdays 11-12 or by appt.
Course website and syllabus: http://www.astro.utoronto.ca/~rayjay/ast251
Astronomy 251
Life on Other Worlds
TAs:
Parandis Khavari khavari@astro A-GTim Rothwell rothwell@cita H-NMarija Stankovic stankovic@astro P-Z
Course Textbook
Goldsmith & Owen
The Search for Life in the Universe
Latest news…
Planetary debris disks aroundyoung Sun-like stars
Latest news…
Cassini at Saturn(NASA/ESA joint mission)
layers of haze in Titan’s upper atmosphere
Titan close-up: “Xanadu” and clouds
Latest news…
Cassini at Saturn
Huygens probe released December 25 Will arrive at Titan January 14, and (hopefully!) descend through its thick, smoggy atmosphere
Latest news…
Mars Express (ESA) continues mapping the red planet
Olympus Mons
and a stereo view of its caldera
Evidence of lava flows within the past two million years…
Could some volcanoes be dormant rather than dead?
Latest news…
Receding glaciers in Alaska
Comparison with photos taken as far back as 1883
Of a thousand glaciers in Alaska, only 15 are still growing; rest are stagnant or melting dramatically
Likely culprit: general warming by at least 1.5o C in the 20th century
Toboggan glacier:
in 1909 and 2000
Latest news…
Microbes deep under the ocean floor
New evidence of microbe communities as much as 0.5 km below the ocean floor (core samples taken off Peru in the Pacific Ocean)
These microbes seem to rely ultimately on oxygen and organic matter produced by photosynthesis
Speculation on Extraterrestrial Life
In religion…
Vedda culture (indigenous to Sri Lanka)After death, souls migrate to the Sun, the Moon, and the stars.
Church of Latter-Day Saints (Mormon Church) Souls move to the celestial kingdom; the worthy create new worlds.
Speculation on Extraterrestrial Life
Early scientific speculation…
Greek philosophersBoth Materialists and Idealists held that life extended beyond Earth.
c. 600 BCE Thales of Miletus (first Greek philosopher?) The Earth and stars are made of the same material.
c. 450 BCE AnaxagorasThe Moon is inhabited.
Speculation on Extraterrestrial Life
Epicurian school introduces panspermia: “ubiquitous life”
c. 400 BCE Metrodorus of Chios (atomist; student of Epicurus) “It is unnatural in a large field to have only one shaft of wheat and in the infinite universe only one living world.”
c. 50 BCE Titus Lucretius Carus "Nothing in the universe is unique and alone, and therefore in other regions there must be other Earths inhabited by different tribes of men and breeds of beasts."
Speculation on Extraterrestrial Life
c. 1590 Giordano Bruno (Italian monk)
“Innumerable suns exist; innumerable earths revolve around these suns in a manner similar to the way the seven planets revolve around our sun…”
in De l'Infinito , Universo e Mondi
Burned at stake for his heretical beliefs on February 17, 1600 in Rome
Speculation on Extraterrestrial Life
1750-1830: speculations by writers (de Bergerac, Voltaire, Lomonosov), philosophers (de Fontenelle, Kant), & scientists (Laplace, Herschel, Huygens, Gauss) on panspermia. Herschel: Thinks Sun is inhabited (also held by Newton!)
1820: Karl Gauss suggests planting trees in a right triangle, demonstrating the Pythagorean Theorem to Martians.
1840: Joseph von Littrow suggests kerosene-filled trenches instead.
1853: A caution on habitability: William Whewellouter planets – “water, gases, and vapour” inner planets – “hot water” on surfaces due to proximity to Sun
Speculation on Extraterrestrial Life
c. 1870: Cammille Flammarion writes On the Plurality of Habitable Worlds.
1896: Konstantin Tsiolkovskiy (early rocket scientist)extraterrestrials may be at different stages of development.
1899: Nikola Tesla sends out burst of radio noise, listens for a reply.
LowellEdison
Tesla
Marconi
Speculation on Extraterrestrial Life
c. 1900: Svante Arrhenius (Swedish chemist): Suggests that spores travel among worlds, seeding life.
Speculation on Extraterrestrial Life
1869: Secchi (Italian Astronomer) sees “canali” on Mars.
1877: Schiaparelli describes seasonal variation in “canali”
1900: Percival Lowell suggests “canals” are large-scale engineering structures and extrapolates an entire culture.
Speculation on Extraterrestrial Life
1922 G. Marconi listens for radio signals from a boat in a remote oceanic location.
1960s - now: Fred Hoyle (deceased), N.C. Wickramsinghe argue life – including infectious diseases viruses – fall on Earth from space.
2003…BBC
Big Questions
Class poll...
Big Questions
1. How did life begin and evolve here on Earth?
2. Does life exist elsewhere in the Universe?
3. What is life’s future, on Earth and beyond?
Big Questions
1. Understand how life arose here2. Determine the principles governing the organization of
matter into living systems3. Explore how life evolves on the molecular, organism, and
ecosystem levels4. Determine how the biosphere co-evolves with the Earth5. Establish limits for life in environments that provide
analogues for conditions on other planets6. Determine what makes a planet habitable and how common
these worlds are7. Determine how to recognize the signature of life on another
planet8. Determine if there ever was or even is life elsewhere in the
Solar System – especially on Mars, Europa, or Titan
Big Questions What is life? How did it come about? How does life affect its environment? How does complex life evolve? ...or intelligence?
How many stars & planets?How far apart?What makes a place hospitable to life?What do we learn about other worlds from our own history?
Did life begin on Earth or did it come from elsewhere?Did life start here only once? How long will it last? How many intelligent civilizations are within earshot? ...or within reach? Is the Galaxy colonized? Where is everybody?
Astrobiology & Bioastronomy
AstronomyGeology Geophysics
CosmologyGalaxy EvolutionStar FormationInterstellar MediumAstrochemistry Stellar EvolutionPlanet FormationPlanetary DynamicsEarth/Moon SystemImpact HistoryExternal HazardsSearch for Extraterrestrials
Biology Prebiotic ChemistryAlternate BiochemistryFormation of LifeEvolution & AdaptationLimits of Life Habitability
Creation of CrustOrigins of OceansOxygen AtmosphereGeothermal HeatPlate TectonicsCO
2 – Silicate Cycle
Course Overview
Origin of the Universe, Stars, and PlanetsIntroduction to our GalaxyStellar Evolution and Creation of the Elements
Formation and early evolution of Earth Geological evolution of Earth Beginnings of life on Earth
Life in extreme environments Habitable environments in the Solar SystemHabitable environments and life in the Galaxy
Interstellar communicationInterstellar travel Colonization of the Milky Way?
Grading
25% Midterm Exam
15% Participation
30% Research Paper
30% Final Exam
Research Paper
Jan 31: statement of intents due1 week later: projects should be approved
Topic suggestions available on website
Feb 28: paper outline due
Mar 14: paper itself due
Drake's Equation(1961 Green Bank meeting)
An estimate of the number of inhabited, communicating planets in the Galaxy
Who's out there?
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Number of stars in the Galaxy: 1011
Lifetime of Galaxy: 1010 years
Star birth rate…
1011 stars/1010 years
~ 10 stars/year
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of Sun-like stars
1961 view: fs ~ 1/10
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of stars with planets
1961 view: fp ~ 1/2
Principle of Mediocrity
D.Durda
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Number of Earth-like planets per extra-solar system
1961 view: ne ~ 1
Again, Principle of Mediocrity
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of Earth-like planets on which life arises
1961 view: fl ~ 1
Yet again, Principle of Mediocrity… plus a look at our own past
Who's out there?
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of biospheres that develop an intelligent species
1961 view: Some intelligence is a good survival trait. So perhaps
fi ~ 1
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of intelligent species that develop technological civilizations and want to communicate
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Fraction of intelligent species that develop technological civilizations and want to communicate
1961 view: fc ~ 1/5
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Typical lifetime of technological civilizations…
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
Typical lifetime of technological civilizations…
L = ?L > 50 yr L < 1010 yr
N = R * fs * fp * ne * fl * fi * fc * L
Drake's Equation
Who's out there?
N = R * fs * fp * ne * fl * fi * fc * L
N ~ 10/year * 1/10 * 1/2 * 1 * 1 * 1 * 1/5 * L years
N ~ L/10
L ~ 50 yr
L ~ 109 yr
To those everywhere who seek to make a large number….
-Walter Sullivan dedication in We are Not Alone (1970)
L
Preview of Lecture 2
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